Peptide biological activity, polymer

Proteins are biologically active polymers of amino acids connected by peptide bonds. 

With the above-mentioned variety of addition reactions based on the addition-elimination mechanism almost any functional group or molecule can be attached to CgQ. Some examples are acetylenes [43, 52], peptides [53], DNA-fragments [53], polymers [54], macrocycles [55, 56], porphyrins [56, 57], dendrimers [58-60] or ligands for complex formation [56], Cjq can be turned into hybrids that are biologically active, water soluble, amphiphilic or mixable with polymers [53-55, 58, 61-69],... 

Oxidizing polymers and polymer-supported carbanion equivalents, in particular, have been employed successfully for preparation of protease inhibitor collections as a practically relevant example. With peptide aldehydes and differently substituted a-hydroxy-jS-amino carbonyl moieties two inhibitory motifs have been prepared with hitherto unprecedented ease and efficiency. Now it remains to be demonstrated that the synthetic methodology as introduced here is capable of assisting the identification of novel biologically active structures. 

The polymer reagent method has been used in peptide synthesis by other investigators also 95 -97). The method has been applied to the synthesis of a number of medium-sized peptides and biologically active protein sequences 98). 

The points that interest us in the study of cyclic peptides are that the models equipped with several features of biopolymers can be constructed, and that the synthetic cyclic peptides are capable of being biologically active substances. In these respects a further development of the study on cyclic peptides is expected in a future. As is obviously seen in this article, emphasis has been placed on the conformational study of cyclic peptides. The author, who is a polymer organic chemist, hopes that the syntheses of biologically active cyclic peptides and cyclic peptide catalysts will be developed. The point that should be pursued most urgently is the synthesis of cyclic peptides capable of catalyzing asymmetric reactions. 

The polymerization of insuHn and proinsulin to dimers and hexamers is a very important process which takes place in the pancreas and impacts upon the pharmaceutical application of insuHn, because the dissociation of the polymers is the rate-limiting processes in the absorption and action in the tissues of the biological active monomeric insulin [45]. The polymerization diminishes osmotic pressure and hy-drophobicity and improves solubility. A positive correlation between expression yield and the degree of polymerization was found [46] that supports yeast in vivo polymerization of insulin precursors and accentuates its importance. However, polymerization can also account for a drawback by retention of product in the vacuole [47]. Intracellular retention of a substantial quantity of the synthesized insulin precursor indicated that the insulin precursor followed two different intracellular routes in the late secretory pathway [12, 47]. Constitutive secretion to the culture supernatant may reflect saturation of a sorting mechanism in the late Golgi due to overexpression. The kexin cleaves the leader-insulin precursor peptide in a late Golgi compartment to yield free insulin precursor, and... 

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